The structure of the core part of Proteus mirabilis O27 lipopolysaccharide with a new type of glycosidic linkage.

The structural assignment of the intact lipopolysaccharide core from Proteus mirabilis O27 has been completed based on a combination of chemical degradation studies, NMR spectroscopy and ES-MS spectroscopy. The overall core structure is as follows: [formula: see text] where all sugars are in the pyranose form except the N-acetylglycosamine residue, Hep refers to L-glycero-alpha-D-manno-heptopyranose and alpha-DDHep to D-glycero-alpha-D-manno-heptopyranose. Bold italics indicate non-stoichiometric substituents. A new type of glycosidic linkage has been discovered wherein a GalNAc residue is linked as an open form acetal to the 4- and 6-positions of a 2-amino-2-deoxygalactopyranose residue. This structural element is abbreviated GaloNAc-4,6-, where the 'o' indicates the open form of the sugar residue.